/***************************************************************************** * vlc_bits.h : Bit handling helpers ***************************************************************************** * Copyright (C) 2001, 2002, 2003, 2006, 2015 VLC authors and VideoLAN * $Id: 395a789eba46ac42413f5fb5418619332589f824 $ * * Authors: Laurent Aimar * Gildas Bazin * Rafaël Carré * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation; either version 2.1 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with this program; if not, write to the Free Software Foundation, * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA. *****************************************************************************/ #ifndef VLC_BITS_H #define VLC_BITS_H 1 #include /** * \file * This file defines functions, structures for handling streams of bits in vlc */ typedef struct bs_s { uint8_t *p_start; uint8_t *p; uint8_t *p_end; ssize_t i_left; /* i_count number of available bits */ bool b_read_only; /* forward read modifier (p_start, p_end, p_fwpriv, count) */ uint8_t *(*pf_forward)(uint8_t *, uint8_t *, void *, size_t); void *p_fwpriv; } bs_t; static inline void bs_write_init( bs_t *s, void *p_data, size_t i_data ) { s->p_start = (uint8_t *)p_data; s->p = s->p_start; s->p_end = s->p_start + i_data; s->i_left = 8; s->b_read_only = false; s->p_fwpriv = NULL; s->pf_forward = NULL; } static inline void bs_init( bs_t *s, const void *p_data, size_t i_data ) { bs_write_init( s, (void*) p_data, i_data ); s->b_read_only = true; } static inline int bs_pos( const bs_t *s ) { return( 8 * ( s->p - s->p_start ) + 8 - s->i_left ); } static inline int bs_remain( const bs_t *s ) { if( s->p >= s->p_end ) return 0; else return( 8 * ( s->p_end - s->p ) - 8 + s->i_left ); } static inline int bs_eof( const bs_t *s ) { return( s->p >= s->p_end ? 1: 0 ); } #define bs_forward( s, i ) \ s->p = s->pf_forward ? s->pf_forward( s->p, s->p_end, s->p_fwpriv, i ) : s->p + i static inline uint32_t bs_read( bs_t *s, int i_count ) { static const uint32_t i_mask[33] = { 0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff, 0x1ff, 0x3ff, 0x7ff, 0xfff, 0x1fff, 0x3fff, 0x7fff, 0xffff, 0x1ffff, 0x3ffff, 0x7ffff, 0xfffff, 0x1fffff, 0x3fffff, 0x7fffff, 0xffffff, 0x1ffffff, 0x3ffffff, 0x7ffffff, 0xfffffff, 0x1fffffff,0x3fffffff,0x7fffffff,0xffffffff}; int i_shr, i_drop = 0; uint32_t i_result = 0; if( i_count > 32 ) { i_drop = i_count - 32; i_count = 32; } while( i_count > 0 ) { if( s->p >= s->p_end ) { break; } if( ( i_shr = s->i_left - i_count ) >= 0 ) { /* more in the buffer than requested */ i_result |= ( *s->p >> i_shr )&i_mask[i_count]; s->i_left -= i_count; if( s->i_left == 0 ) { bs_forward( s, 1 ); s->i_left = 8; } break; } else { /* less in the buffer than requested */ if( -i_shr == 32 ) i_result = 0; else i_result |= (*s->p&i_mask[s->i_left]) << -i_shr; i_count -= s->i_left; bs_forward( s, 1); s->i_left = 8; } } if( i_drop ) bs_forward( s, i_drop ); return( i_result ); } static inline uint32_t bs_read1( bs_t *s ) { if( s->p < s->p_end ) { unsigned int i_result; s->i_left--; i_result = ( *s->p >> s->i_left )&0x01; if( s->i_left == 0 ) { bs_forward( s, 1 ); s->i_left = 8; } return i_result; } return 0; } static inline uint32_t bs_show( bs_t *s, int i_count ) { bs_t s_tmp = *s; return bs_read( &s_tmp, i_count ); } static inline void bs_skip( bs_t *s, ssize_t i_count ) { s->i_left -= i_count; if( s->i_left <= 0 ) { const size_t i_bytes = 1 + s->i_left / -8; bs_forward( s, i_bytes ); if( i_bytes * 8 < i_bytes /* ofw */ ) s->i_left = i_bytes; else s->i_left += 8 * i_bytes; } } static inline void bs_write( bs_t *s, int i_count, uint32_t i_bits ) { if( s->b_read_only ) return; while( i_count > 0 ) { if( s->p >= s->p_end ) { break; } i_count--; if( ( i_bits >> i_count )&0x01 ) { *s->p |= 1 << ( s->i_left - 1 ); } else { *s->p &= ~( 1 << ( s->i_left - 1 ) ); } s->i_left--; if( s->i_left == 0 ) { bs_forward( s, 1 ); s->i_left = 8; } } } static inline bool bs_aligned( bs_t *s ) { return s->i_left % 8 == 0; } static inline void bs_align( bs_t *s ) { if( s->i_left != 8 ) { s->i_left = 8; s->p++; } } static inline void bs_align_0( bs_t *s ) { if( s->i_left != 8 ) { bs_write( s, s->i_left, 0 ); } } static inline void bs_align_1( bs_t *s ) { while( !s->b_read_only && s->i_left != 8 ) { bs_write( s, 1, 1 ); } } /* Read unsigned Exp-Golomb code */ static inline uint_fast32_t bs_read_ue( bs_t * bs ) { unsigned i = 0; while( bs_read1( bs ) == 0 && bs->p < bs->p_end && i < 31 ) i++; return (1U << i) - 1 + bs_read( bs, i ); } /* Read signed Exp-Golomb code */ static inline int_fast32_t bs_read_se( bs_t *s ) { uint_fast32_t val = bs_read_ue( s ); return (val & 0x01) ? (int_fast32_t)((val + 1) / 2) : -(int_fast32_t)(val / 2); } #undef bs_forward #endif